There are a large number of patent applications describing various aspects of thin film Li-deposition; however the majority pertain to different deposition methods such as pulsed laser deposition, sputtering, and the like. These methods present different issues to which solutions must be found, for instance laser deposition and sputtering may be harmful to the substrate due to the high energy impact of the deposited method upon the substrate. Furthermore these methods are difficult to control in an adequate manner and in such applications wherein layer thickness control is of vital importance the methods may prove difficult to apply. There is additionally the difficulty of providing a defect free or pinhole free layer which is desired in many industrial applications. Such applications may be as an electronic barrier between other materials or layers so that there is no electric leakage across the barrier or in some applications no physical contact between layers whom one desires to separate. By sputtering or by laser deposition techniques it is very difficult to ensure that the entire surface is covered and a defective film may result. An area wherein it is especially important to provide defect free layers is in battery technology wherein lithium-comprising layers are to be separated by electrolytes allowing for the passage of lithium ions, but wherein no physical or electric contact should be made between the layers to avoid an irreversible reduction in the battery efficiency. The layers should preferably be as thin as possible to provide the least resistance to the passage of the ions, and thus layer control is of the utmost importance.
P. Fragnaul et al. in J. Power Sources 54,362 1995 proposes a CVD method for the deposition of thin films of the active cathode materials LiCoO2 and LiMn2O4 by chemical techniques. Low pressure chemical vapour deposition is described as being successful at readily preparing LiCoO2 at temperatures ranging from 450 to 650° C.; however, in order to prepare the spinel phase LiMn2O4, temperatures greater than 600° C. were required. No mention is made of the use of ALD or ALE technology.
WO00/25378 to Menachem et al. describes a method for forming a battery in which CVD techniques are used to form an electrolyte barrier in a Li-solid state battery. However, CVD differs widely from ALD in that CVD and MOCVD are not self-limiting reactions as is ALD, and they are thus more difficult to control. There are also issues in that the reaction temperature must be very closely monitored, and in that there might occur undesirable side reactions whilst performing the deposition. In contrast ALD proposes a simple self-limiting reaction wherein a monolayer of the desired compound may be deposited on a substrate, and wherein each layer formation reaction is self controlled.
US20070026309 to Notten et al. describes a method for forming a solid battery wherein the anode and cathode are separated by an electrolyte. There is a description of the electrolyte layer being a lithium comprising electrolyte wherein said lithium comprising electrolyte is deposited by either Physical Vapor Deposition (PVD), Chemical Vapor Deposition (CVD), and/or Atomic Vapor Deposition (AVD). However there is no mention of how this is to be performed, and the sequential listing of alternative methods for the production of said electrolyte is merely a listing of known gas phase deposition methods. No mention has been found of the authors citing an ALD methodology as described in the present invention elsewhere in the art. On the contrary the authors themselves have in WO2006092747 solely proposed the use of MOCVD in the production of the Li layers, this being a clear indication that the inventors have in fact not used ALD methodology to produce the Li layers. If the authors had proposed the use of ALD in the production of Li comprising layers, they would as persons skilled in the art have recognised the beneficial aspects of the method as such, and would have proposed using ALD instead of MOCVD. EP06710932/WO2006056963 to the same authors are variations on the same theme of the above invention.
U.S. Pat. No. 6,818,517 describe the use of ALD technique to for metal oxide layer and list a considerable number of metals. There is no example which discloses how deposition of Li or La can be accomplished.
US2004/0043149 disclose the deposition of metal silicates or phosphates using CVD and ALD.